An important link exists between the selected molecular structure of a sensitizer and the employed shuttle electrolyte to achieve high conversion efficiency in dye-sensitized solar cells (DSSCs). So far, the most commonly used redox mediator is iodide/triiodide (I − /I 3 − ), which has shown advantages such as desirable kinetic properties and high carrier collection efficiencies. However, it has several disadvantages including a low redox potential, corrosion toward metal materials and competitive blue light absorption. In this respect, the transition metal complex electrolytes represent valuable alternatives to replace with traditional I − /I 3 − couples, which can overcome the drawbacks of I − /I 3 − electrolyte. In recent years, the best efficiency of DSSC was achieved by porphyrin-sensitized solar cells with transition metal complex-based redox electrolyte. In particular, in 2014, the Gratzel group published a record DSSC efficiency of 13 % by using a new porphyrin sensitizer with Co-polypyridyl-based electrolyte. Here, we plan the engineering of structure of new transition metal complex electrolyte and the design of molecular structure of sensitizer in touch. The main focus will be held on the correlation between photophysical and electrochemical properties of the metal complex mediators and their DSSC performances. This review provides an in-depth investigation on the exciting alternative electrolyte shuttle in DSSCs and their various advantages that are endowed with both high conversion efficiency and non-corrosive properties. Fig. 11 Device stability of [Fe(CN)6] 4-/3− mediated devices during light soaking with green (stars) and blue (pentagons) light. The performance parameters a) Voc b) Jsc c) FF and d) efficiency were measured at filtered (480 nm cut off) one sun AM 1.5 light. Reproduced with permission from ref. 85.

Transition Metal Complex Redox Shuttles for Dye-Sensitized Solar Cells -[128 refs.]. -(PASHAEI, B.; SHAHROOSVAND*, H.; ABBASI, P.; RSC Adv. 5 (2015) 115, 94814-94848, http://dx.